1. Field of the Invention
The present invention pertains to apparatus and methods for filling containers with liquid. More specifically, the present invention pertains to drum filling apparatus, and methods of the use thereof, which are provided with a tubular filling lance through which liquid is transferred to a drum and which is vertically moveable by a power device between raised and lowered positions in response to various control signals.
2. Description of the Prior Art
There are many apparatus designs for filling drums with liquid. Some of the most successful and efficient filling apparatuses are those of the type having a tubular filling lance which is operatively connected to a source of liquid and which is vertically moveable by a power device between raised and lowered positions. The lance is positioned above an opening in the drum and lowered into the drum for filling thereof. After the container is filled, the lance is returned to a fully raised and/or withdrawn position.
In many situations, particularly in filling drums with liquids susceptible to foaming, the lance is lowered into the drum to a position just above the bottom of the drum before fluid is introduced through the lance. In early versions of drum fillers, the lance remained totally submerged as the drum was filled to its final capacity. Then the lance was withdrawn from the drum. A number of later drum fillers have been provided with features in which the lower end of the lance would be submerged in the liquid but the lance would be moved upwardly as the drum is filled so that just the lower end of the lance is submerged in liquid until the drum is filled. When the drum is filled to a predetermined amount or weight, then the lance is raised to an uppermost raised position, out of the drum, allowing the filling opening to be plugged and the filled drum to be further handled for shipping and/or storage.
There are several reasons for keeping the lower end of the lance slightly submerged below the surface of the liquid, as it is being introduced into a drum, such as minimizing product contact with air, reducing static electric charges and preventing foaming and splashing. Foaming and splashing may result in less accurate and efficient measuring of liquids and may create additional fumes or vapors which might be more difficult to dispose of. Another reason for keeping only a small portion of the lance submerged in the liquid during filling is to prevent wetting of the rest of the lance with quick setting liquids, making it difficult to remove excess material therefrom and difficult to determine the final weight of the container since a substantial amount might drip from the lance after it is removed from the drum. Even in apparatus and methods in which only the lower end of the lance is submerged in the liquid, wiper rings and drip collectors are frequently provided to minimize this problem.
In most recently designed drum fillers, raising of the lance is in response to weight of fluid in the drum as indicated by a signal transmitted from a scale to a controller. With such apparatus and methods the lance is lowered into the drum to a predetermined position just above the bottom of the drum. Control valves are opened to introduce liquid into the drum and the lance is simultaneously raised, so that its lower end is kept submerged just below the surface of the liquid, until a predetermined weight of liquid is in the drum. Then control valves reduce the flow rate to a dribble-fill rate until a predetermined target net weight of liquid within the drum is reached. Then the control valves are completely closed, terminating flow from the source of liquid. Two of the more recent and successful drum fillers of this type, sometimes referred to as xe2x80x9craise by weightsxe2x80x9d fillers, are disclosed in U.S. Patent Nos. 4,703,780 and 6,053,219.
U.S. Patent No. 4,957,147 discloses a drum filler in which the level of fluid in the drum and ascent of the lance is monitored and controlled by monitoring pressure in a pair of sensor tubes, one to sense when the lance is being withdrawn too quickly and the other to sense when the lance is not withdrawn quickly enough. These tubes pass through the sidewalls of the lance and extend downwardly, one terminating near the bottom of the lance and the other being spaced somewhat above.
Even though these recently designed drum fillers are substantially better than those of the prior art, improvements can be made; particularly in the handling of volatile products and in the tracking or raising of the lance so as to keep only a very small portion of the lance submerged in the liquid. In addition, it is not uncommon for a lance to be lowered into a drum which is already filled, causing a substantial portion of the lance to be coated with the filling material and possibly resulting in spills and overflows. If improvements could be made which would prevent this from happening, it would be well received. Continued improvements are needed.
The present invention provides improved apparatus and methods for filling drums with liquid of a type which has a tubular filling lance operatively connected to a source of liquid and which is vertically moveable between raised and lowered positions. However, the lance in the apparatus and method of the present invention is raised or tracked by a method other than xe2x80x9craise by weightxe2x80x9d. It is raised in response to pressure.
The lance of the present invention is similar to drum filler lances of the prior art in that it is provided with a foot valve which is connected to a rod extending upwardly from the foot valve through the lance to an actuator which reciprocates the rod to open and close the foot valve. However, unlike operating rods of the prior art, the rod of the present invention is tubular and the foot valve is provided with a central port in communication with the interior of the rod. The interior of the tubular rod is in communication, through a conduit, with a pressure transducer which, with associated circuitry, converts pressure to a proportional electrical signal for transmission to control elements for raising the lance.
In operation, the lance is lowered into a drum and the toot valve is opened, allowing fluids to begin filling the drum. As liquid enters the drum and covers the bottom of the lance it creates a pressure within the rod which is transmitted through the conduit to the transducer. When pressure reaches a first predetermined amount, for example two inches of water, the transducer transmits an electrical signal to a controller which sends a signal to a carriage on which the lance is mounted, raising the lance a specified amount but keeping the lower end of the lance and the foot valve submerged beneath the surface of the liquid. As the lance is raised, pressure in the tubular rod is reduced sending a signal to stop raising the lance until liquid again rises in the tubular rod to create a pressure which through the transducer and the electrical circuitry causes the lance to raise again. This process continues so that the lance is raised incrementally until the drum is completely full. As it is raised, only a small portion of the lower end of the lance is submerged in the liquid. Most of the lance is never submerged in the liquid.
In preferred embodiments of the invention, the tubular rod is also in communication with a source of low pressure gas, such as air or an inert gas. Although this feature is not necessary in all cases, its primary purpose is to clear the tubular rod, particularly in the case of very viscous fluids, so that a true pressure is always transmitted to the pressure transducer. If the drum is being filled with a volatile fluid, the gas provided can be an inert gas so that a blanket of inert gas will cover the liquid.
The pressure sensing in the tubular rod of the present invention is primarily for tracking and raising of the lance. However, it also serves as a warning if the drum is completely or partially filled, such being indicated by pressure in the tubular rod as the lance is lowered into the drum. Thus, accidental mixing of products and unwanted coating of the lance is prevented. Many other objects of the invention will be apparent from reading the description which follows in conjunction with the accompanying drawings.